High density tape carrier system and method of operation

ABSTRACT

A flexible carrier tape system, suitable for housing components and for winding on a reel in high density, is disclosed, comprising an elongated base strip having a plurality of longitudinally spaced cavities with side walls having a step-like groove near the surface around the cavity, comprising further an elongated cover strip having a width matching the width of the cavity including the widths of the grooves, the cover strip sealed onto the base strip so that the cover strip rests on the step-like grooves. In one embodiment, the sealed cover strip forms a substantially uniform plane with the upper surface of the base strip. The thickness consumed by each tape winding becomes a minimum so that a high density of components can be stored and transported.

BACKGROUND OF THE INVENTION

[0001] The present invention is related in general to the field ofsemiconductor devices and processes and more specifically to the designand operation of tape carriers for high density storage and transport ofsemiconductor devices.

DESCRIPTION OF THE RELATED ART

[0002] Many semiconductor devices are packed by the manufacturer, andthen transported to the customer, in carrier tapes wound onto a reel.Cavities are embossed into the tape to form pockets designed accordingto industry standards; in each pocket is commonly accommodated onesemiconductor device of given size and configuration.

[0003] When the carrier tape is covered by a cover tape, industrystandards such as EIA 481-1, 481-2, and 481-3 regulate the design of thetape pockets. A number of patents have tried to address the problems ofplacing an electronic component into the cavities securely and preventany unforeseen movement of the component which could damage itssensitive parts. Other patents discussed options of covering thecavities for protection and transportation.

[0004] In U.S. Pat. No. 5,648,136, issued on Jul. 15, 1997 (Bird,“Component Carrier Tape”), the design of a flexible carrier tape forstorage and delivery of components, and the advancement mechanism of thetape system are described. Aligned pockets in the tape have an adhesivethermoplastic elastomer on the bottom wall in order to retain thecomponents in the pockets. It is difficult for the proposed system tomeet the stringent storage and delivery reliability requirements ofadvanced semiconductor devices, and to allow easy component removal bythe customer for rapid component assembly.

[0005] These difficulties are not resolved in the follow-up proposals inU.S. Pat. Nos. 5,729,963, issued on Mar. 24, 1998 (Bird, “ComponentCarrier Tape”), and 5,846,621, issued on Dec. 8, 1998 (Nagamatsu,“Component Carrier Tape Having Static Dissipative Properties”). In thelatter patent, a layer of static dissipative acrylic polymer is added tothe strip portion of the carrier system. The cover is releasably,adhesively bonded to the strip portion, covering a plurality of pockets.The acrylic polymer is also used to reduce the temperature at which thecover is bonded to the strip portion.

[0006] The problem of sealing the cover tape to the component carriertape is addressed by radically opposite approaches in the following twopatents: U.S. Pat. No. 5,234,104, issued on Aug. 10, 1993 (Schulte etal., “Carrier Tape System”), describes a cover strip having a topsurface and opposed side walls extending downwardly from the topsurface. The opposed sidewalls are spaced apart from each other adistance substantially equal to the width of the base strip. The coverstrip further includes retaining means formed integrally therewith formechanically engaging and holding down thin component parts seated incavities formed in the base strip. The retaining means is comprised of apair of spaced apart rail members which are formed coextensive with thecover strip extending longitudinally to the sidewalls and projectingdownwardly and outwardly from the top surface thereof. The rail membersare flared outwardly at a slight angle toward the respective opposedsidewalls. The proposed solution is expensive, impractical to assembleby the manufacturer and impractical to unload by the customer.

[0007] U.S. Pat. No. 5,931,337, issued on Aug. 3, 1999 (Ando et al.,“Semiconductor Accommodating Devices and Method for Inserting and TakingOut Semiconductor Devices”), describes an embossed tape, wound on areel, without using the customary top cover tape. The embossed tape hasa bottom wall for placing a semiconductor device thereon, two sidewallsupwardly extending from both side edges of the bottom wall, and topwalls having an opening. The sidewalls are formed such that thesemiconductor device inserted through the opening is held by thesidewalls with the semiconductor device placed on the bottom wall. Thearrangement is inflexible for geometrical changes of the deviceoutlines, and the reliability of transportation is questionable.

[0008] An urgent need has therefore arisen for a coherent, low-costmethod of fabricating a carrier tape, wound onto a reel in high density,with a cover tape reliably sealed to the carrier tape. The method shouldbe flexible enough to be applied for different semiconductor productfamilies, should allow high density packing and tape winding, and shouldachieve improvements toward the goal reliably inserting and extractingsmall outline and low profile packages. Preferably, these innovationsshould be accomplished using the installed equipment base so that noinvestment in new manufacturing machines is needed.

SUMMARY OF THE INVENTION

[0009] According to the present invention, a flexible carrier tapesystem, suitable for housing components and for winding on a reel inhigh density, is disclosed, comprising an elongated base strip having aplurality of longitudinally spaced cavities with side walls having astep-like groove near the surface around the cavity, comprising furtheran elongated cover strip having a width matching the width of the cavityincluding the widths of the grooves, the cover strip sealed onto thebase strip so that the cover strip rests on the step-like grooves.

[0010] In one embodiment, the sealed cover strip forms a substantiallyuniform plane with the upper surface of the base strip. The thicknessconsumed by each tape winding becomes a minimum.

[0011] In another embodiment, the cover strip rests in the step-likegrooves and also on the top surface of the housed components. Anymovement of the components is impeded.

[0012] In yet another embodiment, the cover strip bulges around the topsurface of the housed components, pressuring them onto the bottom wallof the cavities. Any movement of the components is prevented.

[0013] The present invention is related to any products of type andsize, which can be stored and delivered in cavities in plastic tapes. Aprominent group of these products include electronic components andsemiconductor devices. Among the semiconductor devices, components canbe found in many integrated circuit families such as standard linear andlogic products, processors, digital and analog devices, high frequencyand high power devices, and both large and small area chip categories.The invention is equally useful to semiconductor manufacturers anddevice users, which may be found in cellular communications pagers, harddisk drives, laptop computers and medical instrumentation.

[0014] By way of example and using the familiar acronyms for identifyingsemiconductor devices, the invention applies predominantly to devicesfrom the product families of TSOP, SOIC, SSOP, TSSOP, TVSOP, BGA,rectangular as well as square QFP, TQFP, LQFP, and CSP (chip-scale andchip-size packages); it further applies to SOT23, TO-220, and TO-89packages, and many more.

[0015] It is an aspect of the present invention to provide a technologyfor maximizing the amount of tape windings fitting on a reel, and thusthe amount of product, housed in plastic cavities in the tape, storedand delivered per reel. The aspect is achieved by designing step-likegrooves around the storage cavities in the base strip so that the coverstrip can rest in these grooves and form a substantially uniform planewith the upper surface of the base strip.

[0016] Another aspect of the invention is to provide a method ofpreventing movement of the stored components without using adhesives.This aspect is achieved by applying the cover strip under slightpressure to the housed component.

[0017] Another aspect of the invention is to increase product quality tothe customer by eliminating damage due to handling, a common problem instoring and delivering components.

[0018] Another aspect of the invention is to introduce packing conceptsfor a wide variety of components which are flexible so that they can beapplied to many product families, especially of electronic andsemiconductor types, and are general so that they can be applied toseveral future generations of products.

[0019] Another aspect of the invention is to provide a low-cost,high-speed process for fabrication with minimum movement of parts andproduct in the assembly equipment, and reach these goals withoutequipment changes and using the installed fabrication equipment base.

[0020] The technical advances represented by the invention, as well asthe aspects thereof, will become apparent from the following descriptionof the preferred embodiments of the invention, when considered inconjunction with the accompanying drawings and the novel features setforth in the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

[0021]FIG. 1 is a schematic and simplified perspective view of a reelwinding a flexible carrier tape including a base strip having cavitiesand a cover strip.

[0022]FIG. 2A is a schematic top view of the embossed base strip ofFIG. 1. FIG. 2B is a cross sectional view of a cavity in the base stripfor housing components.

[0023]FIG. 3 is a schematic and simplified cross section of a cavity inthe base strip of the carrier tape according to the first embodiment ofthe invention.

[0024]FIG. 4 is a schematic and simplified cross section of a cavity inthe base strip of the carrier tape according to the second embodiment ofthe invention.

[0025]FIG. 5 is a schematic and simplified cross section of a cavity inthe base strip of the carrier tape according to the third embodiment ofthe invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0026]FIG. 1 depicts a tape and reel configuration, generally designated10, as commonly used in many industries for storage and transport ofproducts from the manufacturer to the customer. The prominent examplefor this invention is the semiconductor industry. The tape and reelconfiguration is designed for feeding electronic components such assemiconductor devices to automatic placement machines in the customerhouse for board assemblies. Commonly, surface mount technology isemployed; consequently, the tape is designed to be suitable for surfacemount semiconductor packages.

[0027] A flexible carrier tape 11 is wound on a reel 12, preferably inhigh density. For most applications, the carrier tape 11 comprises anelongated base strip 13 and elongated cover strip 14. The cover strip issealed to the base strip along the edges. In base strip 13, a pluralityof cavities 15 is embossed, preferably equally spaced in longitudinaldirection. Base strip 13 has an upper surface 13 a; the cavities 15extend downward from this upper surface 13 a to a predetermined depthsuitable for housing components such as semiconductor devices. The factof the embossed cavities is indicated in FIG. 1 by the curved bending oftape wall 16.

[0028] The tape material suitable for the base scrips of this inventionis typically polystyrene or polystyrene lamin,ate, preferably in athickness range from about 0.2 to 0.4 mm (unformed film), dependentlargely on the size and weight of the component to be carried by thetape. The cover strip may be the same material yet thinner, or anothermaterial selected such that the strip sealing temperature remainspreferably in the range 150 to 200° C. These materials are commerciallyavailable from suppliers worldwide. In the USA, examples are thecompanies Advantek, ITW, Expotech and Martinez; in Japan, Dainippon andShin Etsu; in Korea, SVM and Allkey; in Malaysia, C-Pak and ITW; inSingapore, Dou Yee and Sumicarrier; in the Philippines, ITW.

[0029] After the composite tape 11 is loaded with the components andsealed, it is wound onto reel 12. The reel is placed into a corrugatedshipping box for transport and delivery.

[0030] The base strip 13 of carrier tape 11 is illustrated in moredetail by example of FIGS. 2A and 2B, with examples for design,dimensions, and component types tabulated in Table 1 of the Appendix.FIG. 2A shows in top view base strip 20 having width 21 (called “W” inTable 1 of the Appendix). Embossed in base strip 20 is a plurality ofcavities 22. They are preferably uniformly spaced by pitch 23 (called“P” in Table 1) in longitudinal direction. Each cavity is characterizedby length 24 (called “X” in Table 1) and width 25 (called “Y” in Table1). For square shaped cavities, length 24 and width 25 have the samedimensions; for round cavities, a diameter is substituted for length andwidth. Holes 29 are needed to index the carrier tape in thepick-and-place machines in the end-user's assembly line.

[0031]FIG. 2B is created by cross sectioning one of the cavities in FIG.2A along line “2B-2B” . The figure illustrates the depth 26 (called “D”in Table 1) of the cavity. The cavity is shown in FIG. 2B in schematicmanner, having a flat bottom wall and sidewalls substantially with onlysmall inclination. As FIGS. 3 to 5 show in more detail, however, thebottom wall has preferably a plurality of ridges for engaging the storedcomponents.

[0032] Pivotally important for the present invention are the grooves 27of FIG. 2A. They have a step-like configuration, as shown in more detailin FIGS. 3 to 5, and serve to support the cover strip (designated 28 inFIG. 2B) for easy sealing. The grooves extend continuously from onecavity to the next along the whole length of the carrier tape.

[0033] As the schematic cross section of a carrier tape cavity in FIG. 3indicates, the step-like grooves 31 are near the surface 32 a of thebase strip 32 forming the cavity. The grooves surround, at leastpartially, the cavity and are located where the cavity side walls 33meet with surface 32 a. In FIG. 3, the cavity is generally designated30; it represents the first embodiment of the present invention. Thepurpose of the grooves is to offer a secure location for resting thecover tape 34. This means that the depth 31 a of the grooves has to besufficient for the thickness of cover tape 34 (typically between 0.02and 0.08 mm). The cover tape can then be placed so that its surface 34 aforms a substantially uniform plane with the upper surface 32 a of thebase strip.

[0034]FIG. 3 further illustrates that the bottom wall 35 of the cavityhas a plurality of ridges 36 disposed in the bottom portion of thecavity. They serve to engage peripheral portions 37 of the components38, stored in the cavity, at predetermined lateral positions within thecavity. FIG. 3 shows that a small distance 39 remains as a gap betweenthe surface of the stored component 38 and the cover strip 34. The totaldepth 33 a of the cavity is predetermined to house component 38 in thecavity which rests on the ridges 36. Numerical examples of depth 33 aare compiled as parameter “D” in Table 1 of the Appendix. For thedistance 36 a, which takes account of the height of the ridges 36,numerical examples are compiled as parameter “E” in Table 1.

[0035] Since cover strip 34 forms a substantially uniform plane withsurface 32 a; depth 33 a defines the radial distance consumed by eachtape winding on the reel of FIG. 1. This solution permits the maximumnumber of tape windings per reel diameter and thus provides a highdensity tape carrier system.

[0036] The second preferred embodiment of the present invention isdepicted in the schematic cross section of FIG. 4. In contrast to FIG.3, the height 46 a of the ridges 46, supporting component 48, iselevated so that there is no gap 49 left between the surface of thestored component 48 and the cover strip 44. Consequently, the topsurface of component 48 is contacting cover strip 44, mechanicallyengaging component 48 in order to impede any movement of the component.The component is thus confined into its position in the cavity.

[0037] The third preferred embodiment of the present invention isdepicted in the schematic cross section of FIG. 5. In contrast to theembodiments illustrated in FIGS. 3 and 4, the depth 53 a of thesidewalls 53 is reduced (the depth 53 b denotes the dimension of thesidewalls in FIGS. 3 and 4). For constant height 56 a of the bottomridges 56 of the cavity, this reduction of side wall depth causes theupper surface 58 a of the stored component 58 to protrude over the uppersurface 52 a of the base strip 52. Consequently, the cover strip 54 hasto be applied under slight mechanical pressure against component 58 sothat it can rest in the step-like grooves 51. After sealing of the coverstrip 54 to the carrier base strip 52, the mechanical pressure isreleased. By spring-like action from the ridges 56, the component 58rebounds against cover strip 54 and pushes it slightly upward. As aconsequence, cover strip 54 slightly bulges around the top surface 58 aof component 58. The component is thus confined into its position in thecavity and any unwanted movement of the component is prevented.

[0038] While this invention has been described in reference toillustrative embodiments, this description is not intended to beconstrued in a limiting sense. Various modifications and combinations ofthe illustrative embodiments, as well as other embodiments of theinvention, will be apparent to persons skilled in the art upon referenceto the description. As an example, the material of the semiconductorchip in the electronic components may comprise silicon, silicongermanium, gallium arsenide, or any other semiconductor material used inmanufacturing. As another example, the ridges supporting the electroniccomponent in the tape cavities may have a number of different shapes,including one or more holes in the plastic material. As another example,the components stored and transported in the cavities may be differentobjects from cavity to cavity, or may originate from a variety ofproduction realms. It is therefore intended that the appended claimsencompass any such modifications or embodiments. TABLE 1 Reel Component# diameter X Y D E P W Family P/N [mm] [mm] [mm] [mm] [mm] [mm] [mm]SOIC 8 330 6.4 5.2 2.1 N/A 8 12 14 330 6.5 9 2.1 N/A 8 16 16 330 6.510.3 2.1 N/A 8 16 16 330 11.1 10.85 2.65 2.35 12 16 20 330 11.1 13.352.7 2.35 12 24 24 330 11.1 15.9 2.7 2.35 12 24 28 330 11.35 18.67 3.12.44 16 32 TSSOP 8 330 7 3.6 1.6 1.2 8 12 14 330 7 5.6 1.6 1.2 8 12 16330 7 5.6 1.6 1.2 8 12 20 330 6.95 7.1 1.6 1.2 8 16 24 330 6.95 8.3 1.61.2 8 16 48 330 8.6 15.8 1.8 1.3 12 24 56 330 8.6 15.8 1.8 1.3 12 24 64330 8.4 17.3 1.7 1.2 12 24 SOP 8 330 8.2 6.6 2.5 2.1 12 16 14 330 8.210.5 2.5 2.1 12 16 16 330 8.2 10.5 2.5 2.1 12 16 20 330 8.2 13 2.5 2.112 24 24 330 8.2 ?? 2.5 2.1 12 24 SSOP 14 330 8.2 6.6 2.5 2.1 12 16 16330 8.2 6.6 2.5 2.1 12 16 20 330 8.2 7.5 2.5 2.1 12 16 24 330 8.2 8.82.5 2.1 12 16 28 330 8.2 10.5 2.5 2.1 12 16 30 330 8.2 10.5 2.5 2.1 1216 38 330 8.2 13 2.5 2.1 12 24 28 330 11.35 9.78 3.1 2.44 12 24 48 33011.35 16.2 3.1 2.44 16 32 56 330 11.35 18.67 3.1 2.44 16 32 16 330 6.45.2 2.1 N/A 8 16 20 330 6.5 10.3 2.1 N/A 8 16 24 330 6.5 10.3 2.1 N/A 816 TVSOP 14 330 6.8 4 1.6 1.2 8 12 16 330 6.8 4 1.6 1.2 8 12 20 330 75.6 1.6 1.2 8 12 24 330 7 5.6 1.6 1.2 8 12 48 330 6.8 10.1 1.6 1.2 12 2456 330 6.8 11.7 1.6 1.2 12 24 80 330 8.4 17.3 1.7 1.2 12 24 TQFP 64 33012.5 12.5 1.9 1.6 16 24 Powerflax 2 330 6.5 10 2.45 2.2 8 16 3 330 9.811 2.45 2.2 12 24 5 330 9.8 11 2.45 2.2 12 24 PLCC 20 330 10.3 10.3 4.93.8 12 16 28 330 13 13 4.9 3.7 16 24 44 330 18 18 5.7 4.1 24 32MicroStarBGA 96 330 5.7 13.7 2 1.2 8 24 114 330 5.7 16.2 2 1.2 8 24 SOT3 330 4.85 4.52 2.3 1.85 8 12 5 178 2.24 2.34 1.22 n/a 4 8 5 178 3.153.2 1.4 n/a 4 8 TO-92 3 360 n/a n/a n/a 13 18 paper tape

I claim:
 1. A flexible carrier tape system, suitable for winding on areel in high density, comprising: an elongated base strip having anupper surface and a plurality of longitudinally spaced cavitiesextending downwardly a predetermined depth from said upper surface forhousing components therein; each of said cavities having sidewalls and abottom wall, said sidewalls having a step-like groove near said surfacearound said cavity, and said bottom wall having a plurality of ridgesdisposed therein for engaging peripheral portions of said componentsdisposed within said cavities, for confining said components atpredetermined lateral positions within said cavities; an elongated coverstrip having a width matching the width of said cavity including thewidths of said grooves; and said cover strip sealed onto said base stripso that said cover strip rests in said step-like grooves around saidcavities and forms a substantially uniform plane with said uppersurface, whereby said predetermined cavity depth exclusively defines theradial distance consumed by each tape winding on said reel.
 2. Thecarrier system according to claim 1 wherein said cavities have a formselected from a group consisting of cuboid, cubic, cylindrical andsemispherical shape.
 3. The carrier system according to claim 1 whereinsaid base strip and said cover strip are made of a material selectedfrom a group consisting of polystyrene, polystyrene laminate, or otherpolymers suitable for a sealing temperature between 150 and 200 ° C. anda thickness range from about 0.2 to 0.4 mm.
 4. The carrier systemaccording to claim 1 wherein said components are semiconductor devices.5. A flexible carrier tape system, suitable for winding on a reel inhigh density, comprising: an elongated base strip having an uppersurface and a plurality of longitudinally spaced cavities extendingdownwardly to a depth from said upper surface equal to the thickness ofcomponents to be housed therein; each of said cavities having sidewallsand a bottom wall, said sidewalls having a step-like groove near saidsurface around said cavity, and said bottom wall having a plurality ofridges disposed therein for engaging peripheral portions of saidcomponents disposed within said cavities, for confining said componentsat predetermined lateral positions within said cavities; an elongatedcover strip having a width matching the width of said cavity includingthe widths of said grooves; and said cover strip sealed onto said basestrip so that said cover strip rests in said step-like grooves aroundsaid cavities, forming a substantially uniform plane with said uppersurface, and concurrently contacts the top surface of said components,whereby said components are mechanically engaged to impede movement. 6.A flexible carrier tape system, suitable for winding on a reel in highdensity, comprising: an elongated base strip having an upper surface anda plurality of longitudinally spaced cavities extending downwardly to adepth from said upper surface slightly less than the thickness ofcomponents to be housed therein; each of said cavities having sidewallsand a bottom wall, said sidewalls having a step-like groove near saidsurface around said cavity, and said bottom wall having a plurality ofridges disposed therein for engaging peripheral portions of saidcomponents disposed within said cavities, for confining said componentsat predetermined lateral positions within said cavities; an elongatedcover strip having a width matching the width of said cavity includingthe widths of said grooves; and said cover strip sealed onto said basestrip so that said cover strip rests in said step-like grooves aroundsaid cavities, bulging around the top surface of said components andpressuring said components onto said bottom ridges, whereby movement ofsaid components prevented.